1. Technical Field of the Invention
This invention relates generally to wireless communication systems and more particularly to wireless communication devices.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, ZigBee, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), radio frequency identification (RFID), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, RFID reader, RFID tag, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system or a particular RF frequency for some systems) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
As is also known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
In many applications of a radio transceiver, the raw data that is transmitted and/or received includes digitized audio signals (e.g., digitized voice, music files such as MP3 files, video files such as MPEG files, and/or a combination thereof). As is known, a microphone is used to capture analog audio signals and a speaker is used to render analog audio signals audible. As is known, analog audio signals captured by a microphone are biased to a particular level, amplified, and digitized (i.e., converted to digital signals and may further be encoded in accordance with an encoding format). As is further known, digitized audio signals are converted to analog audio signals, amplified via a volume control, and subsequently rendered audible by a speaker.
Recently, through the advent of Microelectromechanical Systems (MEMs), a few companies have developed microphone integrated circuits and speaker integrated circuits. For example, Akustica, as claimed on its web page (Akustica.com), has developed an analog microphone chip (part no. AKU1000), a digital microphone chip (part no. AKU2000), and speaker chips. While integrated microphone chips and speaker chips offer communication device manufacturers smaller form factors, the chips are still separate components requiring printed circuit board (PCB) space and connections to and/or from other integrated circuits on the PCB.
Therefore, a need exists for a radio frequency integrated circuit that includes an on-chip acoustic transducer circuit.